High voltage substation for metropolitan areas



April 16, 1968 D. L. WHITEHEAD 3,378,731

HIGH VOLTAGE SUBSTATION FOR METROPOLITAN AREAS Filed July 26, 1965 '7 Sheets-Sheet 1.

l KV 38 J30 i F!G.l.

April 16, 1968 D. 1.. WHITEHEAD HIGH VOLTAGE SUBSTATION FOR METROPOLITAN AREAS '7 Shee cs-Sheet Filed July 26, 1965 FIG.3-

GOO

(DOC) GGCkOGG GGC) WITNESSES OINVENTOR Daniel L. Whitehead ATTO MGM- RNEY April 16, 1968 D. L. WHITEHEAD I 3,373,731

HIGH VOLTAGE SUBSTATION FOR METROPOLITAN AREAS Filed July 26, 1965 '7 Sheets-Sheet 5 April 16, 1968 D. WHITEHEAD 3,378,731

HIGH VOLTAGE SUBSTATION FOR METROPOLITAN AREAS Filed July 26, 1965 '7 Sheets-Sheet 4 FIGS.

April 1968 D. L. WHlTEHEAD 3,378,731

HIGH VOLTAGE SUBSTATION FOR METROPOLITAN AREAS Filed July 26, 1965 "(Sheets-Sheet 33 5 22 38 o FIG-6.

M ;fl .fl 3?\ 38 v 34 I I I HIGH VOLTAGE SUBSTATION FOR METROPOLITAN AREAS 7 Sheets-Sheet 7 Filed July 26, 1965 Fill l- M m F. w N A a W k O 75 3 4 \xy 4 f 3 6 5 4 United States Patent 3,378,731 HIGH VOLTAGE SUBSTATION FOR METROPOLITAN AREAS Daniel L. Whitehead, Franklin Township, Export, Pa., as-

signor to Westinghouse Electric Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Filed July 26, 1965, Ser. No. 474,779 4 Claims. (Cl. 317-103) ABSTRACT OF THE DISCLOSURE This invention relates, generally, to electric power distribution and, more particularly, to high voltage substations. More specifically, the components of a substation including a transformer, circuit breakers and disconnect switches are mounted at different vertically spaced levels in a sectionalized structure. All of the high voltage conductors interconnecting the components of the substation are enclosed in grounded conducting pipes containing a pressurized high dielectric insulating medium, such as SP gas. The components of the substation are mounted above as well as alongside the transformer to permit short bus runs with the components above the transformer be ing supported on a framework.

The power demands of some of our large metropolitan cities have reached such proportions that it is now necessary to transmit power into such cities at 345,000 volts with the possibility of eventually going to much higher voltages. Present practice is to use a cable system under the city streets with risers to outdoor substations and switchyards. The switchyards comprise disconnect switches, circuit breakers, lightning arresters, transformers and auxiliary apparatus so connected as to provide electrical service to local areas. With prior substation construction techniques, the area required for a typical 345 kv. substation is indeed large. Engineers at an electric utility company in one of our large cities have estimated that a 345 kv. substation to serve a certain portion of the city would require 17 acres of land. Such large areas simply are not available in that district.

An object of this invention is to provide a high voltage substation construction which requires only about of the land area required for prior substations.

Another object of the invention is to provide a substation structure which is suitable for installing underground.

A further object of the invention is to provide a substation structure in which all energized parts are enclosed by grounded conducting sheaths or pipes, thereby precluding the possibility of personnel coming into contact with high voltage conductors.

Still another object of the invention is to provide a sectionalized substation structure in which all units of the station can be factory built and then connected with a minimum of effort when installed.

A still further object of the invention is to prevent corona at the joints between the insulators and the conductors and between the insulators and the pipes which enclose the conductors and the insulators for supporting the conductors inside the pipes.

Another object of the invention is to provide a sealed joint for connecting together sections of the enclosing pipe.

A further object of the invention is to provide for repressurizing a gas-insulated sectionalized substation structure up to a point where a section of the structure is removed for maintenance.

Other objects of the invention will be explained fully hereinafter or Will be apparent to those skilled in the art.

ice

In accordance with the invention, the components of a substation, including a transformer, circuit breakers, disconnect switches, lightning arresters, coupling capacitors and auxiliary apparatus are so mounted as to provide a compact sectionalized structure. All conductors are enclosed in grounded conducting pipes containing a pressurized high dielectric insulating medium, preferably SF gas. The conductors are supported in the pipes by generally disc-shaped insulators. The disconnect switches, circuit breakers and other components are included in the pressurized gas system and are mounted above as well as alongside the transformer to permit short bus runs and minimize space requirements. A suitable framework supports the components mounted above the transformer. The sectionalized construction permits all units of the substation to be factory built and then connected with a minimum of effort in the field. Any element needing repair or service can be easily removed and replaced with a spare. Various sections can be bolted or welded together.

For a better understanding of the nature and objects of the invention, reference may be had to the following detailed description, taken in conjunction with the accompanying drawings, in which:

FIGURE 1 is a single line diagram of a typical ring bus electric power distribution system;

FIG. 2 is a view, in plan, of a scale model of a structure containing the substation components encompassed by the dot-dash lines in FIG. 1;

FIGS. 3, 4, 5 and'6 are views in front, rear, right side and left side elevation, respectively, of the structure shown in FIG. 2;

FIG. 7 is a view, partly in elevation and partly in section, of a lightning arrester and enclosing housing utilized in the structure;

FIG. 8 is a view, similar to FIG. 7, of a terminal for the substation transformer;

FIG. 9 is a view, in section, of an insulator for supporting the conductor in the pipe;

FIG. 10 is a view, in section, of another insulator;

FIG. 11 is a view, in section, of a bonnet for capping the end of a conductor and pipe when a section of the structure is taken out of service;

FIG. 12 is a view, in section, of a bolted joint for connecting two sections of the enclosing pipe together;

FIG. 13 is a sectional view taken along the lines XIII XIII in FIG. 12; and

FIG. 14 is a view, in section, of a welded T-joint for connecting sections of the enclosing pipe together.

Referring to the drawings, and particularly to FIG. 1, the single line diagram illustrates a typical ring bus commonly used in high voltage substations. The ring bus system includes an incoming line disconnect switch 10, a bustie circuit breaker 11 and associated disconnect switches 12 and 13, an incoming line circuit breaker 14 and associated disconnect switches 15 and 16, a transformer 17 and associated disconnect switches 18 and 19, lightning arresters 21 and 22, coupling capacitors 23, bus sectionalizing circuit breakers 24, 25, 26, 27 and disconnect switches associated with the bus sectionalizing breakers, an additional feeder transformer 28 and its associated disconnect switches and lightning arrester and an additional feeder circuit 29. It will be understood that additional apparatus similar to that shown could be included in the power distribution system. The portion of the substation apparatus included within the dot-dash rectangle 30 is represented by the scale model illustrated in FIGS. 2 to 6, inclusive. Since the distribution system is a three-phase system, the model includes three of each one of the items shown within the rectangle 30 with the exception of the transformer 17 which contains the three-phase windings Within one housing.

As shown most clearly in FIGS. 3 to 6 inclusive, the substation apparatus is arranged in three levels. The transformer 17, its cooling radiators 31, the disconnect switches 19 and the lightning arresters 21 are mounted on one level. The circuit breakers 14, disconnect switches 15 and 18, and the coupling capacitors 23 are mounted on the first level above the transformer 17. The circuit breakers 11, the disconnect switches 12 and 13 and the lightning arresters 22 are mounted on the second level above the transformer 17. The apparatus above the level of the transformer is supported by a suitable framework which includes vertical members 32, horizontal tie members 33 and horizontal support members 34 which rest on the tie members 33.

The present circuit breakers are of the dead tank type. They may be generally of the gas-blast type disclosed in a copending application Ser. No. 61,284, filed Oct. 7, 1960, by R. G. Colclaser and R. N. Yeckley which issued Oct. 27, 1964 as U.S. Patent 3,154,658 and assigned to the Westinghouse Electric Corporation. The contact members and interrupting unit for each phase are enclosed in a generally cylindrical tank. The tank contains an interrupting medium, such as sulfur hexafluoride, SP gas at a relatively low pressure. The SP gas is stored at a relatively high pressure in reservoirs 35 and admitted to the interrupting units of the circuit breakers through blast valves during an interrupting operation.

The disconnect switches are of the reciprocating type, such as the switch disclosed in a copending application Ser. No. 474,155, filed July 26, 1965, now Patent No. 3,348,001, by George Siviy and C. W. Upton which was issued Oct. 17, 1967 as U.S. Patent 3,348,001 and assigned to the Westinghouse Electric Corporation. The contact members for each phase are enclosed in a generally cylindrical metal housing containing a gas, such as SP which has a high dielectric strength, thereby making it particularly suitable for the present application. The lightning arresters and coupling capacitors may be of a type well known in the art. The lightning arrester for each phase is enclosed in a metal housing containing SF gas. Likewise, the coupling capacitor for each phase is enclosed in a separate metal housing containing SP gas.

As shown most clearly in FIGS. and 6, the circuit breakers 11 and their associated disconnect switches 12 and 13 are arranged in an inverted U-formation, the upper ends of the disconnect switch housings being joined to the tanks of their respective circuit breakers. Auxiliary apparatus, such as relays 36', gas storage chambers 37 and operating mechanism housings 38, is mounted between the legs of the U formed by the circuit breakers 11 and the disconnect switches 12 and 13.

As also shown in FIGS. 5 and 6, the circuit breakers 14, their associated disconnect switches 15 and 16, and the disconnect switches 18 are arranged in a rectangular formation with auxiliary apparatus such as the relays 36, gas storage chambers 37 and operating mechanism housings 38 mounted inside the rectangle formed by the circuit breaker and the disconnect switches. In this manner the substation apparatus is mounted in a compact arrangement so as to require a minimum amount of space.

The transformer and the disconnect switches are interconnected by conductors each one of which is enclosed in a grounded conducting housing containing a high dielectric strength gas, such as SF Other gases such as carbon dioxide, nitrogen and even air or various mixtures of these gases may be utilized if desired. However, SP is particularly suitable in view of its high dielectric strength. The gas maintained in the enclosing pipes with respect to the size of the conductor inside the pipe will depend upon the operating voltage, the dielectric strength of the insulating medium and the pressure at which the medium is maintained. By operating at a pressure of approximately 15 pounds p.s.i.g., no special pressure vessel codes need be considered. In some cases the additonal cost of meeting pressure vessel codes required for the higher pressures would dictate the use of the lower pressures with the corresponding increase in size of the conductor housings. In other cases where space is at a premium, the additional cost of meeting pressure codes would be justified.

The pipes which enclose the conductors are preferably composed of a good conducting metal, such as aluminum. However, the pipes may be made from one of the modern plastics, particularly for lower pressure operations. In case plastic pipes are utilized, the outside of each pipe should be coated with a good conducting or semiconducting material to ensure that it would be at ground potential as a safety measure.

As shown in the drawings, the substation is so arranged that it can be built in sections at a factory and then installed with a minimum of effort. Thus, sectionalized apparatus in one level is connected to corresponding sectionalized apparatus in another level through suitable conductors enclosed in the pipe housings. Suitable joints or junctions are provided for connecting sections of the apparatus together. Also, any element needing repair or service can be easily removed and replaced with a spa-re.

In order to facilitate the sectionalizing of the substation structure, sections of the pipes which enclose the conductors can be bolted or welded together by utilizing joints or junctions 41 and 42. As shown in FIG. 12, the joint 41 is suitable for connecting two coaxial sections of pipe 43 together. As shown in FIG. 14, the T-shaped joint 42 is suitable for connecting three sections of pipe, one of which is disposed at a right angle to the two coaxial sections. Each section of pipe 43 has a flange 44 at its end with a rim 45 extending beyond the flange 44. A coupling member 46 has a flange 47 at each end. A portion of each flange 47 overlaps the rim 45 on the end of one of the pipe sections 43. An O-ring seal 48 is provided to prevent gas leakage when the flanges are bolted together by means of bolts 49. In order to provide access to the joint between sections of a conductor 50 or 51 inside of the pipe 43, the coupling member 46 is divided longitudinally and provided with flanges 52 which are bolted together by bolts 49 as shown in FIG. 13.

In the T-shaped joint 42 shown in FIG. 14, the coupling member 46' is divided into three pieces, thereby providing for connecting three sections of pipe 43, one of which is disposed at a right angle to the two sections. The flanges on the pipe and the coupling members may be joined by welds 53. The rims 45 prevent any weld head or waste material from entering the system. To open the welded joint it is necessary to grind off the exterior Weld. However, the flanges are sufliciently wide to permit this to be done a number of times if required.

The conductors 51 may be joined by welding or by compression fittings of the type described in a copending application Ser. No. 474,799, filed July 26, 1965. As previously stated, the coupling members are divided to permit them to be removed to provide access to the joints between the conductors 51.

If it is necessary to remove a section of bus or other apparatus, a bonnet 54 may be attached to the end of the pipe 43 as shown in FIG. 11. In this manner the pipe is capped or closed to permit re-pressurizing of the system up to that point. As shown, the bonnet 54 is generally spherical in shape to minimize voltage gradients and has a flange 55 which may be attached to the flange 44 on the end of the pipe 43 by means of bolts 49.

In order to prevent corona at the end of the conductor 51 a generally spherical member 56 may be attached to the end of the conductor. The member 56 has a stem 57 with a reduced portion 58 which may be inserted into the end of the hollow conductor 51, thereby retaining the member 56 in position inside the spherical bonnet 54.

The disconnect switches, the circuit breakers, the lightning arresters and other components are included in the pressurized gas system. As shown in FIG. 7, a lightning arrester 21 is connected to a conductor 51 and enclosed by a pipe 43 the end of which may be attached to a floor or support 61 by means of a flange 44. As previously stated, the arrester 21 may be of a well known type and provided wth a grading ring 62, if required.

In case the transformer 17 contains oil or a nonfiammable liquid 63, it is necessary to prevent the gas in the pressurized system from entering the transformer tank. As shown in FIG. 8, a terminal bushing 64- provides for the transition between gas on one side and transformer oil on the other. The lower portion 65 of the bushing extending into oil is grooved in the usual manner to increase creepage distance along the surface of the bushing. The upper section 66, which is surrounded by the high dielectric strength gas is shorter and has a smooth surface. A conductor '67 extends through the bushing and is connected to a conductor 51 at the upper end of the bushing. A suitable shield 68 surrounds the connection between the two conductors. A current transformer 69, which may be of the conventional bushing type, may be provided. Gas leakage is prevented by suitable seals between the flange 44 on the pipe 43 and the transformer tank to which the flange 44 is attached. Likewise, gas leakage into the' tank is prevented by a seal between the flanged ring 71 and the tank where the ring is attached to the tank to support the bushing 64.

,In some cases it may be desirable to operate the disconnects and breakers at a different gas pressure, or even with a different gas, than that of the bus runs. In such cases, terminal connections similar to the transformer connection may be utilized. Gas pressure is maintained on the system by a suitable gas supply and compressor system. Simplicity can be attained by using a common gas supply for the entire system. However, if the common system includes the circuit breakers, filtering and cleaning must be included to remove the products of combustion caused by the interrupting action of a circuit breaker. Such filtering and cleaning systems are well known in the art.

One critical problem that arises in a pressurized system of the present type is the proper construction of the insulators which support the conductors inside the pressurized pipes. With the high voltage gradients involved particular attention must be paid to the joints between each insulator and conductor and the insulator and the pressure pipe, or between an insulator and a ground return conductor if one is used. Normally, the joint between the insulator and the central conductor is the critical one since the stresses are higher there. If epoxy, or other resin material, is used for the insulator, a good joint can be made by molding the insulator to the conductor and using generous fillets at the point of connection. If porcelain or glass is used for the insulators, the problem becomes more critical. Tests have shown that even very small separations between the insulator and the conductor result in l-owvalues of breakdown voltage. This problem can be solved by filling the void between the insulator 75 and the conductor 51 with plastic material 76, such as epoxy, as shown in FIG. 9.

Another and better solution is shown in FIG. 10, where the space is filled with a rubber compound grommet 77. Carbon-filled neoprene, which is a conducting resilient material, is suitable for this application. The grommet is beveled at 78 to minimize the voltage gradient in the critical areas. With a normal dielectric constant of approximately one-half of that of the insulator disc, a favorable dielectric grading results. The elasticity of the rubber compound also distributes and relieves mechanical stresses between the insulator and the conductor, particularly those occurring during assembly and during short-circuit fault conditions. A similar ring grommet 79 is disposed between the outer rim of the insulator 75 and the inner periphery of the pipe 43.

The high gradients at the edge of the insulator junction with the conductor may also be reduced by providing shielding members 81 around the conductor '51 adjacent the grommet 78. The shielding members 81 have the effect of placing the insulator 75 down in a slot or recess, thereby reducing the high gradients in a manner described in a copending application, Ser. No. 474,774, filed July 26, 196 5 by D. F. Shankle and L. A. Kilgore which was issued June 6, 1967, as US. Patent 3,324,272 and assigned to the Westinghouse Electric Corporation. Similar shielding rings 82 may be provided around the inner periphery of the pipe 43 adjacent the grommet 79. Likewise, shielding rings 81 and 82 may be provided adjacent the insulator shown in FIG. 9.

The same problems involving return paths and their associated losses are present in the compact substation as in the transmission system described in the aforesaid copending application Ser. No. 474,799. One solution consists of simply making the pressure pipe from good conducting, non-magnetic material, such as aluminum, with sufficient crosssection to keep the losses to an acceptable value. If steel pipes are used, a return liner or its equivalent, as described in the aforesaid copending application, can be used.

Since all exposed parts of the system are at ground potential, no shock hazards are present and the entire substation can be installed indoors, underground, or in basement areas under large buildings. No fire hazard exists, with the possible exception of the transformer which may be filled with oil, or preferably a nonflammable liquid, in the event gas filled transformers are not used. If the transformers are oil filled they can be isolated by a fireproof vault type construction without greatly increasing the space requirements.

From the foregoing description it is apparent that the invention provides a substation construction which has numerous advantages, one of the most important of which is the drastic reduction in space required for this substantion. Furthermore, the present structure does not necessarily require surface land area at all, since it is ideally suited for sub-basement or underground construction. Also, the new structure provides greatly improved safety features. Being totally enclosed, there is no possibility of personnel coming into accidental contact with high voltage lines. The enclosed construction makes the station lightning proof as well as virtually sabotage and bombproof. Radio interference no longer exists with its nuisance to residents as well as possible interference with airborne navigation equipment.

Since numerous changes may be made in the abovedescribed construction and different embodiments of the invention may be made without departing from the spirit and scope thereof, it is intended that all subject matter contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

I claim as my invention:

1. A sectionalized electrical substation comprising a transformer mounted at a first horizontal level; a first group of enclosed circuit breakers and associated enclosed disconnect switches mounted at a second horizontal level vertically spaced from the first level and above the transformer, a second group of enclosed circuit breakers and associated enclosed disconnect switches mounted at a third horizontal level vertically spaced from the second level and above the transformer, a framework supporting said first and second groups of circuit breakers and disconnect switches in vertically spaced relation above the transformer and including vertically spaced horizontal sup-porting members corresponding to at least said second and third levels and to an additional horizontal level above said second group of circuit breakers and disconnect switches, said first group of circuit breakers being disposed entirely between said second and third horizontal levels and said second group of circuit breakers being disposed entirely between said third horizontal level and said additional horizontal level, conductors interconnecting the transformer and the disconnect switches, each conductor being enclosed in a grounded conducting 7 pipe containing a gas of high dielectric strength, and connecting joints between sections of said pipes to permit the substation to be built in predetermined sections and then connected together.

2. A sectionalized electrical substation comprising a tnansformer at a first horizontal level, circuit breakers and associated disconnect switches mounted at a second horizontal level vertically spaced from the first level and above the transformer, a frame-work for supporting the circuit breakers and the disconnect switches in vertically spaced relation above the transformer andincluding vertically spaced horizontal supporting members corresponding to at least said second level and an additional horizontal level above the second level, a generally cylindrical tank enclosing the contacts of each circuit breaker, a generally cylindrical housing enclosing the contacts of each disconnect switch, the tank of each circuit breaker and the housings of two of its associated disconnect switches being joined in an inverted U-formation disposed entirely between said second level and said additional horizontal level, auxiliary apparatus mounted between the legs of the U-formation, conductors interconnecting the transformer and the disconnect switches, and each conductor being enclosed in a grounded conducting pipe containing a gas of high dielectric strength.

3. A sectionalized electrical substation comprising a transformer mounted at a first horizontal level, a first group of enclosed circuit breakers and associated enclosed disconnect switches mounted at a second horizontal level vertically spaced from the first level and above the transformer, a second group of enclosed circuit breakers and associated enclosed disconnect switches mounted at a third horizontal level vertically spaced from the second level and above the transformer, a framework supporting said first and second groups of circuit breakers and disconnect switches in vertically spaced relation above the transformer and including vertically spaced horizontal supporting members corresponding to at least said second and third levels and to an additional horizontal level above said second group of circuit breakers and disconnect switches, the circuit breakers and the disconnect switches at one level being disposed in a rectangular formation, auxiliary apparatus mounted within the rectangular formation, said first group of circuit breakers being disposed entirely between said second and third horizontal levels and said second group of circuit breakers being disposed entirely between said third horizontal level and said additional horizontal level, conductors interconnecting the transformer and the disconnect switches, and each conductor being enclosed in a grounded conducting pipe containing a gas of high dielectric strength.

4. A sectionalized electrical substation comprising a transformer mounted at a first horizontal level, a first group of enclosed circuit breakers and associated enclosed disconnect switches mounted at a second horizontal level vertically spaced from the first level and above the transformer, a second group of enclosed circuit breakers and associated enclosed disconnect switches mounted at a third horizontal level vertically spaced from the second level and above the transformer, a framework supporting said first and second groups of circuit breakers and disconnect switches in vertically spaced relation above the transformer and including vertically spaced horizontal supporting members corresponding to at least said second and third levels and to an additional horizontal level above said second group of circuit breakers and disconnect switches, the circuit breakers and the disconnect switches of one of said groups being disposed in a rectangular formation, auxiliary apparatus mounted within-the rectangular formation, the circuit breakers and the disconnect switches of the other of said groups being disposed in an inverted U-formation, auxiliary apparatus mounted between the legs of the U-formation, said first group of circuit breakers being disposed entirely between said second and third horizontal levels and said second group of circuit breakers being disposed entirely between said third horizontal level and said additional horizontal level, conductors interconnecting the transformer and the disconnect switches, and each conductor being enclosed in a grounded conducting pipe containing .a gas of high dielectric strength.

References Cited UNITED STATES PATENTS 3,235,774 2/1966 [Frowein 317-4033 ROBERT K. SCHAEFER, Primary Examiner.

J. R. SCOTT, Assistant Examiner. 

